MongoDB提供了mongoexport工具，可以把一个collection导出成json格式或csv格式的文件。可以指定导出哪些数据项，也可以根据给定的条件导出数据。工具帮助信息如下：

[root@localhost bin]# ./mongoexport --help  
options:  
--help produce help message   
-v [ --verbose ] be more verbose (include multiple times for more   
verbosity e.g. -vvvvv)   
-h [ --host ] arg mongo host to connect to ( /s1,s2 for sets)   
--port arg server port. Can also use --host hostname:port   
--ipv6 enable IPv6 support (disabled by default)   
-u [ --username ] arg username   
-p [ --password ] arg password   
--dbpath arg directly access mongod database files in the given   
path, instead of connecting to a mongod server -   
needs to lock the data directory, so cannot be used   
if a mongod is currently accessing the same path   
--directoryperdb if dbpath specified, each db is in a separate   
directory   
-d [ --db ] arg database to use   
-c [ --collection ] arg collection to use (some commands)   
-f [ --fields ] arg comma separated list of field names e.g. -f name,age   
--fieldFile arg file with fields names - 1 per line   
-q [ --query ] arg query filter, as a JSON string   
--csv export to csv instead of json   
-o [ --out ] arg output file; if not specified, stdout is used   
--jsonArray output to a json array rather than one object per   
line   
[root@localhost bin]#

下面我们将以一个实际的例子说明，此工具的用法：

将foo库中的表t1导出成json格式：

[root@localhost bin]# ./mongoexport -d foo -c t1 -o /data/t1.json   
connected to: 127.0.0.1   
exported 1 records   
[root@localhost bin]#

[root@localhost data]# more t1.json   
{ "_id" : { "$oid" : "4f927e2385b7a6814a0540a0" }, "age" : 2 }   
[root@localhost data]#

[root@localhost bin]# ./mongoexport -d foo -c t2 --csv -f age,name -o /data/t2.csv   
connected to: 127.0.0.1   
exported 1 records   
[root@localhost bin]#

查看/data/t2.csv的导出结果：

[root@localhost data]# more t2.csv   
age,name   
1,"wwl"   
[root@localhost data]#

mongoimport导入工具

[root@localhost bin]# ./mongoimport --help   
options:   
--help produce help message   
-v [ --verbose ] be more verbose (include multiple times for more   
verbosity e.g. -vvvvv)   
-h [ --host ] arg mongo host to connect to ( /s1,s2 for sets)   
--port arg server port. Can also use --host hostname:port   
--ipv6 enable IPv6 support (disabled by default)   
-u [ --username ] arg username   
-p [ --password ] arg password   
--dbpath arg directly access mongod database files in the given   
path, instead of connecting to a mongod server -   
needs to lock the data directory, so cannot be used   
if a mongod is currently accessing the same path   
--directoryperdb if dbpath specified, each db is in a separate   
directory   
-d [ --db ] arg database to use   
-c [ --collection ] arg collection to use (some commands)   
-f [ --fields ] arg comma separated list of field names e.g. -f name,age   
--fieldFile arg file with fields names - 1 per line   
--ignoreBlanks if given, empty fields in csv and tsv will be ignored   
--type arg type of file to import. default: json (json,csv,tsv)   
--file arg file to import from; if not specified stdin is used   
--drop drop collection first   
--headerline CSV,TSV only - use first line as headers   
--upsert insert or update objects that already exist   
--upsertFields arg comma-separated fields for the query part of the   
upsert. You should make sure this is indexed   
--stopOnError stop importing at first error rather than continuing   
--jsonArray load a json array, not one item per line. Currently   
limited to 4MB.

> db.t1.find();   
{ "_id" : ObjectId("4f937a56450beadc560feaa9"), "age" : 5 }   
>

t1其中有一条age=5的记录, 我们再看一下json文件中的数据是什么样子的：

[root@localhost data]# more t1.json   
{ "_id" : { "$oid" : "4f937a56450beadc560feaa7" }, "age" : 8 }   
[root@localhost data]#

[root@localhost bin]# ./mongoimport -d foo -c t1 /data/t1.json   
connected to: 127.0.0.1   
imported 1 objects

工具返回信息说明向表中插入了一条记录. 我们进库里实际验证一下：

[root@localhost bin]# ./mongo   
MongoDB shell version: 1.8.1   
connecting to: test   
> use foo   
switched to db foo   
> db.t1.find();   
{ "_id" : ObjectId("4f937a56450beadc560feaa9"), "age" : 5 }   
{ "_id" : ObjectId("4f937a56450beadc560feaa7"), "age" : 8 }   
>